Author Topic: Crank Balancing - Do I need to?  (Read 690 times)

Online Russ

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Crank Balancing - Do I need to?
« on: 06.05. 2014 00:39 »
Have been reading and copying your posts on Crank Balancing, thanks KiwiGF.
My question is - Do I need to balance mine?
I have a 52 A10 project which came with the engine partly assembled, however I doubt it ever left the factory as a complete unit.
I will need to fit new oversize pistons but all else is OK. When finished, in the dissssssssstant future, it will only be ridden on sunny Sundays for pleasure.
Any thoughts would be appreciated.

Cheers Russ
1951 A10 Plunger.
Australia

Online Rocket Racer

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Re: Crank Balancing - Do I need to?
« Reply #1 on: 06.05. 2014 01:55 »
As a great believer in "suck it and see" engineering and not being concerned with pulling it down again if I don't like it, I don't typically balance my motors unless they tell me they are unhappy: However my race engine NEEDED balancing and the typical effect of rebores is to reduce balance factor, whereas modern roads typically suggest increasing balance factor.
If you keep your pistons nice and light then it'll quite likely be fine, however if it is apart and you are unsure and you like to pedal hard, then a rebalance is quite sensible.
On my race engine I run short rods and flycut pistons and my balancer suggested the result unchanged was suitable for a stationery motor. The balance certainly cut down vibration breakages and lost bolts.
Just my 10 cents worth
A good rider periodically checks all nuts and bolts with a spanner to see that they are tight - Instruction Manual for BSA B series, p46, para 2.
New Zealand

Offline warmshed

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Re: Crank Balancing - Do I need to?
« Reply #2 on: 06.05. 2014 13:06 »
Balancing unknown components is always worthwhile as its such a pain to assemble and find you have to strip it down and start again.  Once you have the pistons look around for someone you can trust to balance the crank correctly, note the weight of the pistons for future reference in case of a rebore, you can fettle the new pistons to the same weight as your old ones.  If your taking time and money to build a sweet engine its not money wasted.

You may like to look at http://www.a7a10.net/forum/index.php?topic=6086.0  Where it has been discussed and shows a method of doing it yourself.

Online trevinoz

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Re: Crank Balancing - Do I need to?
« Reply #3 on: 06.05. 2014 22:08 »
I have mine dynamically balanced, Russ.
A friend of mine does his own statically with good results.
With dynamic balancing, metal is removed (usually) from exactly where the out of balance is.
Statically, it is usually removed on the centre line of the flywheel.

Trev.

Online Russ

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Re: Crank Balancing - Do I need to?
« Reply #4 on: 08.05. 2014 13:20 »
Thanks Guys,
Sounds like balancing is a good idea so I will look into it.
Appreciate your help.
Russ
1951 A10 Plunger.
Australia